In the prior art, hydrocarbon halide such as trichloroethylene and trichlorotrifluoroethane have been used as an industrial detergent. However, such detergent can not be used today due to a problem of environmental pollution including the destruction of ozone layer.
In view of such a situation, the present applicant developed a halogen-free cleaning composition essentially containing a specific glycol ether compound, a nonionic surfactant and a polyoxyalkylenephosphoric ester surfactant (Japanese Patent No.1832450). A variety of halogen-free detergents heretofore developed contain an ionic surfactant and the like in general and are superior in detergency and in alleviating problems of toxicity, odor, flammability and influence on an article to be cleaned.
With a recent increase in small-size and large-capacity articles to be cleaned, flip chip devices have been increasingly used. Consequently, to finely control the position of parts on the substrate, solder fluxes containing large amounts of additives such as a thickener and a thixotropic agent have grown into use. In this situation, now more excellent detergency is required.
When processed metal parts and ceramic parts are cleaned, there are needs for effectively eliminating particles, grindstone particles, ion components and the like by cleaning in addition to conventional degreasing of processing oils; the above halogen-free detergent may be unsatisfactory in fulfilling the needs.
Halogen-free detergents recently developed are used as follows. After cleaning the article with the halogen-free detergent, the article is subjected to a water-rinsing treatment (generally comprising a step of pre-rinsing the article for removal of dirt components and a succeeding step of finish-rinsing the article for removal of the detergent components), whereby the article can be cleaned to achieve a high extent of cleanliness.
However, when the rinsing water is repeatedly used in such water-rinsing treatment, the rinsing water is thickened with the cleaning components (chiefly an ionic surfactant) and is thereby made alkaline or acidic, so that the materials of article to be cleaned may partly discolor and/or corrode. The discoloration and corrosion of the materials occur at the water-rinsing treatment, especially at the pre-rinsing step for removing the dirt components from the article. For example, a thick coating of glass used in a hybrid IC for vehicles or for communications causes bluing in an acidic aqueous solution and becomes partly dissolved and turned white in an alkaline aqueous solution. Furthermore, the acid or alkali corrodes or discolors portions of metals such as nickel, brass, solder or the like of the surface of the article to be cleaned.